Cutting elements have been utilized for a variety of material removal processes such as machining, cutting, and drilling. For example, tungsten carbide cutting elements have been used for machining metals and, to some degree, on drilling tools for drilling subterranean formations, as known in the art. Further, polycrystalline diamond compact (PDC) cutters have been employed for machining metals (e.g., non-ferrous metals, usually) and for subterranean drilling tools, such as, drill bits, reamers, core bits, etc. Of course, other types of cutting elements have been utilized for cutting operations, for example, ceramic (cubic boron nitride, silicon carbide, etc.) cutting elements or other cutting elements as known in the art.
For example, it is known to perform lathe operations with a cutting element (e.g., PDC cutter, a tungsten carbide cutting element, or another cutting element as known in the art). Additionally, some machinery (i.e., a planer) is designed to remove or cut material along a selected plane by moving a the piece to be cut against a cutting element. In some configurations, the piece to be cut may be rotated and the cutting element may be radially moved to plane or face a surface of the material. Such machinery may be utilized, among other examples, for forming monuments or building materials (e.g., any rock formation, such as granite, marble, etc.).
More particularly, with respect to subterranean drilling, rotary drill bits employing cutting elements for drilling subterranean formations, such as polycrystalline diamond compact (PDC) cutters, have been employed for several decades. Although other configurations are known in the art, PDC cutters are typically comprised of a disc-shaped diamond “table” formed on and bonded (under high-pressure and high-temperature conditions) to a supporting substrate, such as a cemented tungsten carbide (WC) substrate.
As known in the art, the drill bit bodies to which cutting elements are attached may often be formed of steel or of molded tungsten carbide. Drill bit bodies formed of molded tungsten carbide (so-called matrix-type bit bodies) are typically fabricated by preparing a mold that embodies the inverse of the desired topographic features of the drill bit body to be formed. Examples of such topographic features include generally radially extending blades, sockets or pockets for accepting the cutting elements, junk slots, internal watercourses, passages for delivery of drilling fluid to the bit face, ridges, lands, and the like. Tungsten carbide particles are then placed into the mold and a binder material, such as a metal including copper and tin, is melted or infiltrated into the tungsten carbide particles and solidified to form the drill bit body. Steel drill bit bodies, on the other hand, are typically fabricated by machining a piece of steel to form the desired external topographic features of the drill bit body. In both matrix-type and steel bodied drill bits, a threaded pin connection may be formed for securing the drill bit body to the drive shaft of a downhole motor or directly to drill collars at the distal end of a drill string rotated at the surface by a rotary table or top drive.
Cutting elements are typically attached to matrix-type and steel bodied drill bits by either brazing or press-fitting the cutting elements into recesses or pockets formed in the bit face or in blades extending from the face. The cutting elements are attached to the bit bodies in this manner to ensure sufficient cutting element retention, as well as mechanical strength sufficient to withstand the forces experienced during drilling operations. However, conventional drill bits having conventionally attached cutting elements suffer from a number of drawbacks and disadvantages. For example, because the cutting element is affixed to the bit body, only a portion of the circumferential cutting edge of the cutting element actually engages the subterranean formation being drilled. The constant engagement between this select portion of the cutting edge and the formation tends to quickly degrade and wear down the engaged portion of the cutting edge, resulting in decreased cutting element life, drilling efficiency, and accuracy. This constant engagement also significantly increases the temperature of the cutting element, which may further result in increased wear and/or potential destruction of the cutting element and drill bit body.
Accordingly, a number of conventional attempts have been made to provide a drill bit having cutting elements that are free to rotate during drilling due to interaction with a subterranean formation. For example, U.S. Pat. No. 4,553,615 to Grainger (the '615 patent) discloses a rotary drilling drag bit having a cutting element having a spindle formed of cemented tungsten carbide mounted in a recess formed in the face of a bit blade. A similar configuration is disclosed in U.S. Pat. No. 4,222,446 to Vasek.
However, unpredictability of the nature of contact with the formation being drilled, extreme temperatures, forces, and pressures encountered in subterranean drilling environments may prevent or inhibit rotation of the cutting elements altogether. Thus, such a conventional cutting element, as with brazed or press-fit cutting elements, may exhibit a portion of the cutting edge that tends to degrade and wear down, resulting in decreased cutting element life and drilling efficiency. Similarly, when machining, wear that occurs relative to a cutting element may cause interruptions in the machining operation to replace or otherwise reorient the cutting element.
Accordingly, there exists a need for methods and apparatuses for rotating a cutting element during cutting of a material. The torque applied to the cutting element would be sufficient to rotate, either continuously or periodically, the cutting element during cutting of a material.